With progresses in technologies and the development of economy, energies are increasingly consumed in various forms, a huge wireless communication system consists of many portions, among which a Radio Remote Unit (RRU) is an indispensable portion. The RRU includes an RRU equipment and an electric power storage system 1, as shown in FIG. 1.
At present, existing RRUs have an efficiency in an order of 30% or lower. Most energies are lost in the form of thermal energies due to technical limitations of power amplifiers. If the lost thermal energies can be collected and then recycled, we can move a great step towards an environment-friendly communication system advocated by ourselves.